Design and Construction of Hydropower Tunnels in the Upper Lillooet Valley
Renaud De Batz, Claude Chartrand, Innergex Renewable Energy, Vancouver, BC
Serge Moalli, Claude Denault, CRT-EBC, Vancouver, BC
Dean Brox, Dean Brox Consulting, Vancouver, BC
Abstract:
Innergex Renewable Energy is developing two run-of-river hydropower projects in the Upper
Lillooet Valley located approximately 75 km northwest of Pemberton, BC. Both projects are
being executed as design-build risk-sharing contracts following the previous completion of
reference design work. The Upper Lillooet Hydropower will have a capacity of 81.4 MW with a
gross head of 187.4 m and comprise an intake, a 2.5 km, 6 m wide power tunnel of 0.5% grade, a
1.4 km, 3.6 m diameter surface penstock, and a surface powerhouse adjacent to the Upper
Lillooet River. The maximum cover along the tunnel is 210 m. The Boulder Creek Hydropower
will have a capacity of 25.3 MW with a gross head of 297 m and comprise an intake, a 2.8 km,
4m wide power tunnel of 10% grade including a 400 to 450 m long steel liner, a 50 m, 1.6 m
diameter surface penstock, and a surface powerhouse adjacent to Boulder Creek. The maximum
cover along the tunnel is 200 m. Geotechnical investigations were completed for the tunnel
alignment at the Upper Lillooet site and included six drillholes (total 670 m), seismic surveys at
the portals and laboratory testing. Additional investigations have been completed at the intake
and powerhouse locations. Anticipated rock types for the tunnel at the Upper Lillooet site
include poorly welded and welded volcanic breccia, diorite, and meta-volcanics. Only seismic
surveys were completed at the downstream end of the Boulder Creek site and the anticipated
rock type for the tunnel comprises dacites and granodiorites.
Construction of both tunnels at the different sites is planned to commence in mid-2014 and
continue semi-concurrently and be completed in 2016 by drill and blast methods working 24-7
shifts utilizing standard rock support followed by final shotcrete lining as required. The paper
will present design and construction details of the projects including the anticipated and
encountered to date tunnel conditions. The conference presentation will include information on
tunnel construction progress and challenges to date.